This study is designed to elucidate the role of 5-HT activity on the negative feedback mechanisms by glucocorticoids on hypothalamic- pituitary-adrenal axis function in depression. Major hypotheses are: (1) oral administration of mCPP will produce a significant increase in post dexamethasone serum ACTH and cortisol in depression but not in controls; (2) the neuroendocrine ACTH and cortisol responses to mCPP will be positively correlated.